1987 Polaris Indy 400 Repair Manual

The 1987 Polaris Indy 400 is a high-performance snowmobile featuring a 398cc liquid-cooled twin-cylinder engine, CDI ignition system, Mikuni VM34 carburetors, and Polaris Variable Ratio (PVR) suspension. This repair manual covers comprehensive maintenance, troubleshooting, and repair procedures for engine, drive train, suspension, electrical systems, and chassis components. Below are key sections for specifications, maintenance schedules, troubleshooting, and step-by-step repair procedures.

1. Specifications 2. Maintenance Schedule 3. Engine System 4. Fuel System 5. Drive Train 6. Suspension & Steering 7. Electrical System 8. Brake System 9. Troubleshooting Guide 10. Torque Specifications 11. Wiring Diagrams

Specifications

Technical specifications for the 1987 Polaris Indy 400 snowmobile.

Component	Specification
Engine Type	398cc Liquid-cooled twin-cylinder
Bore x Stroke	68mm x 55mm
Compression Ratio	7.5:1
Carburetion	Dual Mikuni VM34
Ignition System	CDI with external coil
Starting System	Electric start with backup recoil
Drive System	Polaris P-85 primary clutch
Track Size	15 x 121 inches
Suspension Front	Polaris Variable Ratio (PVR)
Suspension Rear	Torsion spring with hydraulic shocks

Maintenance Schedule

Regular maintenance intervals for optimal performance and longevity.

Pre-season inspection: Check all systems before first use each season.
Every 500 miles: Change engine oil, inspect drive belt, check track tension.
Every 1,000 miles: Replace spark plugs, clean carburetors, inspect suspension.
Every 2,000 miles: Replace drive belt, check clutch alignment, inspect brakes.
Seasonal storage: Fog engine, stabilize fuel, remove battery for charging.

WARNING! Always disconnect battery before performing electrical work. Use proper safety equipment.

Engine System

Engine repair and maintenance procedures.

Compression test: Remove spark plugs, use compression gauge - should read 120-140 psi.
Cylinder head removal: Drain coolant, remove intake/exhaust, unbolt head.
Piston replacement: Remove cylinder, inspect cylinder walls, replace rings if worn.
Crankcase inspection: Check for oil leaks, inspect seals and gaskets.
Cooling system: Check radiator, hoses, and water pump for proper flow.

CAUTION! Engine components are heavy; use proper lifting equipment. Allow engine to cool before servicing.

Fuel System

Carburetor: Dual Mikuni VM34 with choke and throttle cables.
Fuel Pump: Pulse-operated diaphragm type.
Fuel Filter: In-line filter between tank and pump.
Fuel Lines: Check for cracks and proper routing.
Adjustment: Pilot screw 1.5 turns out, main jet #240.
Cleaning: Disassemble, soak in carb cleaner, blow out passages.
Synchronization: Use vacuum gauges to balance carburetors.

Drive Train

Primary clutch (P-85) and secondary clutch maintenance. Drive belt inspection and replacement procedures.

Primary Clutch: Inspect rollers and weights for wear, clean sheaves with brake cleaner.

Secondary Clutch: Check spring tension, inspect helix for wear patterns.

Drive Belt: Proper tension adjustment, inspection for cracks and wear.

Chaincase: Check oil level, inspect chain and sprockets for wear.

Suspension & Steering

Front PVR suspension and rear torsion spring suspension maintenance.

Front suspension: Check A-arms for cracks, inspect ball joints and bushings.
Shock absorbers: Check for oil leaks, test rebound damping.
Steering linkage: Lubricate tie rod ends, check for play in steering column.
Rear suspension: Adjust torsion spring preload, inspect idler wheels and slides.
Track adjustment: Proper tension (1-1.5 inches free play), alignment check.

Tip: Use thread locker on all suspension fasteners and torque to specifications.

Electrical System

CDI ignition, charging system, and lighting circuits.

Battery: 12V 18Ah, check specific gravity (1.265-1.299), clean terminals.
Stator output: Check AC voltage at various RPM (spec: 14V AC at 3000 RPM).
CDI unit: Test resistance values between terminals per specification chart.
Lighting circuit: Check bulb sockets, wiring harness for corrosion.
Voltage regulator: Test DC output (13.5-14.5V at 3000 RPM).
Starter motor: Check brushes, commutator, and solenoid engagement.

WARNING! Disconnect battery before electrical testing. Use multimeter for accurate measurements.

Brake System

Hydraulic disc brake maintenance and repair.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
Engine won't start	Fuel, spark, or compression	Check fuel delivery, spark plugs, compression test.
Poor performance	Carburetion or clutching	Clean carburetors, inspect clutch components.
Electrical failure	Battery or charging system	Test battery, stator output, voltage regulator.
Overheating	Cooling system blockage	Check coolant level, radiator, water pump.
Track slipping	Drive belt or clutch issues	Inspect belt condition, clutch alignment.

Reset: Disconnect battery for 30 minutes to reset CDI if needed.

Service: Contact Polaris dealer for technical support and genuine parts.

Torque Specifications

Critical fastener torque values for proper assembly.

Wiring Diagrams

Complete electrical schematics for troubleshooting and repair.

Includes: Main harness routing, CDI connections, lighting circuits, charging system wiring, starter circuit diagrams, and switch connections.

CAUTION! Refer to diagrams before modifying electrical system. Use proper wire gauges and connectors.